<!DOCTYPE html>
<html lang="en">
<head>
  <meta charset="UTF-8">
  <meta http-equiv="X-UA-Compatible" content="IE=edge">
  <meta name="viewport" content="width=device-width, initial-scale=1.0">
  <title>Document</title>
  <style>
    .message{
      position: relative;
      top: 100px;

    }
    .count{
      color: white;
      position: absolute;
      top: -15px;
      right: -15px;
      height: 20px;
      background-color: #F56C6C;
      line-height: 20px;
      border-radius: 10px;
      padding: 0 5px;
    }
  </style>
</head>
<body>

  <button class="message">
    消息
    <span class="count">99+</span>
  </button>
</body>
</html>